Broken Chairs

Today while sitting in physics I got the broken chair. I tend to avoid it at all costs but didn't take the same precautionary measures today as i normally do. This normally consists of me sitting in the chair and leaning back to see if it bends, if it does I quickly switch it out for a different one that wont bend back when I lean into it. So today I sat down in my chair and began working instead of leaning back, so when I did lean back about halfway though class, I found my self staring at the ceiling.
So basically I spent half the class leaning forward staring at the board and resting my head on my hands, the other half was spent leaning back staring at the ceiling. Needless to say my back is now killing me because of these two extreme positions. Which then forced me to wonder... why do we keep all these broken chairs around?
I mean it can't be due to lack of chairs because I have seen the teachers hallway and that place is full of unused chairs. Unused UNBROKEN chairs. Why not simply trade out chairs when some lazy bum has bent the chair back so far that an unlazy person who just wants to rest against the back of the chair as they should.
Ok... so the rest of my day was pretty uneventful, except in orchestra we found out we might actually be getting our scores protested from festival which means we could still get a one! So all we have to do is wait to find out on that one...